>You are not forced to look at subreddits that offend you.

I think this is the greatest misconception about the push for de-platforming. The goal is to remove the platform from becoming an echo chamber for racism/hate/violence not to stop people from being offended by content they dislike. By removing mainstream sites as options to promote hatered/racism/violence it's likely that it will make a measurable reduction in people joining these groups as there will be less traffic.